Inner fin and flat tube including an inner fin

ABSTRACT

An inner rib, in particular for a flat tube, in particular of a heat exchanger, made from a metallic flat strip, which is shaped in a wavy modulated manner, having a large number of wave crests and wave troughs, which are each arranged alternately in a longitudinal direction of the inner fin, an essentially straight, web-like fin area being provided between one wave crest and an adjacent wave trough and connecting the wave crest to the wave trough, the metallic flat strip having a first strip thickness L1, which is essentially constant in the area of the wave crests and the wave troughs, the flat metallic strip having a second strip thickness L2, which is provided in the area of the web-like fin area, L2 being smaller than L1.

This nonprovisional application claims priority under 35 U.S.C. § 119(a) to German Patent Application No. 10 2020 201 556.2, which was filed in Germany on Feb. 7, 2020 and which is herein incorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an inner fin and a flat tube, in particular for a heat exchanger, in particular for a motor vehicle.

Description of the Background Art

In heat exchanges for motor vehicles, flat tubes are known, in which an inner fin is inserted or introduced into the tube interior of the flat tube, which abuts and is soldered on the oppositely situated wide sides of the flat tube, so that the flat tube achieves an increased inner pressure resistance. For this purpose, the inner fin is modulated, for example in a wavy manner, including a large number of wave crests and wave troughs, which are each alternately soldered to the wide sides of the flat tube in an abutting manner.

The inner fin improves the inner pressure resistance of the flat tube and also increases the heat transfer rate from a first fluid flowing through the flat tube to a second fluid flowing around the flat tube and back again.

Modern motor vehicles are increasingly optimized for lower consumption values and/or lower emissions. This is particularly true for motor vehicles with internal combustion engines. The orientation toward low consumption values is, however, also highly relevant for electric vehicles or hybrid vehicles, since the low consumption of electrical energy per kilometer driven, in particular, is relevant to the cost of driving the motor vehicle and also determines the maximum range of the motor vehicle.

In this context, however, the focus is on the flat tube in terms of the cost and the weight of the heat exchanger, due to the flat tube's frequent use in a heat exchanger.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an inner fin, which permits a good heat transfer and simultaneously a good inner pressure resistance of a flat tube compared to the prior art, and the inner fin nevertheless being able to be manufactured cost-effectively with a reduced use of materials. The object is also to provide a flat tube including an inner fin, which is cost-effectively strengthened with little use of materials and nevertheless has a good inner pressure resistance and good heat transfer.

An exemplary embodiment of the invention relates to an inner rib, in particular for a flat tube, in particular of a heat exchanger, made from a metallic flat strip, which is shaped in a wavy modulated manner, having a large number of wave crests and wave troughs, which are each arranged alternately in a longitudinal direction of the inner fin, an essentially straight, web-like fin area being provided between one wave crest and an adjacent wave trough and connecting the wave crest to the wave trough, the metallic flat strip having a first strip thickness L1, which is essentially constant in the area of the wave crests and the wave troughs, the flat metallic strip having a second strip thickness L2, which is formed in the area of the web-like fin area, L2 being smaller than L1. Material is thereby saved in an intermediate area between the wave crests and the wave troughs to the extent that a significant weight reduction is achieved, while maintaining a sufficiently good inner pressure resistance and heat transfer.

In one exemplary embodiment, it is advantageous if the metallic flat strip has a first strip thickness L1, which is essentially constant in the entire area of the wave crests and the wave troughs, and the flat metallic strip has a second strip thickness L2, which is essentially formed in the entire area of the web-like fin area. Material is thereby saved in the entire intermediate area between the wave crests and the wave troughs to the extent that a significant weight reduction is achieved, while maintaining a sufficiently good inner pressure resistance and heat transfer.

It is particularly advantageous if the metallic flat strip is curved in the area of the wave crests and the wave troughs. The area of the connection to the flat tube may thereby occur in the curved area, advantageously by soldering.

It is particularly advantageous if strip thickness reduction R from first strip thickness L2 to second strip thickness L2 takes place in a range from 0.2*L1 to 0.9*L1, i.e. 0.2*L1<L2<0.9*L1, in particular 0.3*L1<L2<0.7*L1 or further in particular 0.35*L1<L2<0.55*L1 or further in particular L2=0.5*L1. The intended objectives with respect to inner pressure resistance, material savings as well as with regard to an improvement in the pressure drop in the tube interior are achieved thereby.

It is also expedient if the metallic flat strip has two oppositely situated wide sides, between which the strip thickness may be determined, strip thickness reduction R from first strip thickness L1 to second strip thickness L2 being carried out on at least one wide side of the flat strip or being carried out on both oppositely situated wide sides of the flat tube. An asymmetrical or a symmetrical stiffness behavior may be achieved thereby, the arrangement of the strip thickness reduction also depending on the manufacturing of the strip thickness reduction, for example by rolling the metallic strip.

It is also expedient if strip thickness reduction R from L1 to L2 is carried out on both oppositely situated wide sides of the flat tube by a constriction, approximately the same amount of proportional strip thickness reduction R1, R2 of approximately R1=(L1−L2)/2 and R2=(L1−L2)/2 being present. A favorable force distribution in the desired material reduction is achieved thereby.

It is further advantageous if strip thickness reduction R from L1 to L2 is present on both sides of the neutral fibers of the strip, in particular approximately the same amount of proportional strip thickness reduction R1, R2 of approximately R1=(L1−L2)/2 and R2=(L1-L2)/2 is present on both sides of the neutral fibers. A favorable force distribution in the desired material reduction is achieved thereby.

It is also advantageous if the metallic flat strip has a first strip thickness L1, which is essentially constant in the entire area of the wave crests and the wave troughs, and the flat metallic strip has a second strip thickness L2, which is essentially formed in the entire area of the web-like fin area. A favorable force distribution in the desired material reduction is achieved thereby.

An exemplary embodiment of the invention also relates to a flat tube, including a tube wall and a tube interior, the tube wall having two oppositely situated wide sides and two oppositely situated narrow sides, an inner fin according to the invention being arranged in the tube interior, the wave crests abutting one of the two wide sides of the tube wall, and the wave troughs abutting the other of the two wide sides, in particular the wave crests being connected to one of the two wide sides of the tube wall, and the wave troughs being connected to the other of the two wide sides, in particular soldered, welded or glued.

It is advantageous if the wave crests are soldered on one of the two wide sides of the tube wall, and the wave troughs are soldered on the other of the two wide sides, solder menisci made from solder material forming between the strip and the wide sides, the web-like fin area having second strip thickness L2 being arranged between the solder menisci.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes, combinations, and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

FIG. 1 shows a schematic sectional representation of a flat tube;

FIG. 2 shows a schematic partial sectional representation of a flat tube, including an inner fin according to the invention;

FIG. 3 shows a detail of the section of the inner fin; and

FIG. 4 shows a further detail of the section of the inner fin.

DETAILED DESCRIPTION

FIG. 1 shows a sectional view of a flat tube 1, including a tube wall 2 and a tube interior 3. Tube wall 2 is formed, for example, from a sheet material strip 4, which is deformed. Sheet material strip 4 may thus be designed as a folding tube and be soldered, as illustrated, or the flat tube may alternatively also be designed as a welded tube.

Tube wall 2 has two oppositely situated wide sides 5 and two oppositely situates narrow sides 6, which are arranged alternately in a circumferential manner. Flat tube 1 in the illustrated exemplary embodiment is closed on one of the two narrow sides 6, an overlap of end areas of sheet material strip 4 being formed, which overlap each other and are soldered in this location.

An inner fin 7 is arranged in tube interior 3. Inner fin 7 is formed from a metallic flat strip, which is, for example, rolled to form its structure. For example, metallic strip is formed from aluminum, an aluminum alloy, from steel, etc.

Inner fin 7 is provided with a wavy design, formed in a modulated manner, and has a wave structure, which forms a large number of wave crests 8 and wave troughs 9. The large number of wave crests 8 and wave troughs 9 are each alternately arranged in a longitudinal direction of inner fin 7, an essentially straight, web-like fin area 10 being provided between one wave crest 8 and an adjacent wave trough 9, which connects wave crest 8 to wave trough 9. A large number of adjacent web-like fin areas 10 are formed thereby, which divide interior 3 of flat tube 1 into fluid paths 11. Web-like fin areas 10 may be closed over a wide area or be formed with interruptions to permit a cross flow.

Wave crests 8 abut one of the two wide sides 5 of tube wall 2, and wave troughs 9 abut the other of the two wide sides 5. Advantageously and optionally, wave crests 8 are connected to one of the two wide sides 5 of tube wall 2, and wave troughs 9 are connected to the other of the two wide sides 5, in particular soldered, welded or glued.

In one preferred exemplary embodiment, wave crests 8 are soldered on one of the two wide sides 5 of tube wall 2, and wave troughs 9 are soldered to the other of the two wide sides 5, solder menisci 12 made from solder material being formed between the strip of inner fin 7 and wide sides 5 of flat tube 1, as is apparent in FIG. 2.

Web-like fin area 10 is arranged between solder menisci 12 formed on oppositely situated wide sides 5. It is apparent in FIGS. 1 and 2 that the wall thickness of sheet metal strip 4 of tube wall 2 of flat tube 1 is significantly thicker than the wall thickness of metallic flat strip of inner fin 7, i.e., for example it is at least twice as thick, three times as thick or more.

Upon closer observation of inner fin 7, it is apparent in FIG. 2 that the metallic flat strip of inner fin 7 has a first strip thickness L1, which is provided in the area of wave crests 8 and wave troughs 9 and which is essentially constant.

The flat metallic strip of inner fin 7 also has a second strip thickness L2, which is formed in the area of web-like fin area 10, L2 being smaller than L1.

In one advantageous exemplary embodiment, it is optional and expedient if the metallic flat strip of inner fin 7 has a first strip thickness L1, which is essentially constant in the entire area of wave crests 8 and wave troughs 9, the flat metallic strip of the inner fin having a second strip thickness L2, which is essentially provided with a constant design in the entire area of web-like fin area 10.

It is apparent from FIG. 2 that the metallic flat strip of inner fin 7 is provided with a curved design in the area of wave crests 8 and wave troughs 9. The curvature may have a radius of curvature or assume multiple radii of curvature.

The transition from first strip thickness L1 to second strip thickness L2 advantageous takes place in the transition from curved wave trough 9 to essentially straight, web-like rib area 10 and advantageously takes place in the transition from curved wave crest 8 to essentially straight, web-like fin area 10, as is also apparent in FIG. 2.

Strip thickness reduction R from first strip thickness L1 to second strip thickness L2 takes place in a range from 0.2*L1 to 0.9*L1, i.e. 0.2*L1<L2<0.9*L1. It is particularly advantageous if strip thickness reduction R from first strip thickness L1 to second strip thickness L2 is in a range from 0.3*L1 to 0.7*L1, so that 0.3*L1<L2<0.7*L1, or it is further advantageous if strip thickness reduction R from first strip thickness L1 to second strip thickness L2 is in a range from 0.35*L1 to 0.55*L1, and 0.35*L1<L2<0.55*L1. It may also be advantageous if L2=0.5*L1.

Upon closer examination, the metallic flat strip of inner fin 7 has two oppositely situated wide sides 13, between which the strip thickness may be determined, strip thickness reduction R from first strip thickness L1 to second strip thickness L2 being carried out on at least one wide side 13 of the flat strip of inner fin 7 or, as illustrated in FIGS. 2 through 4, is carried out on both oppositely situated wide sides 13 of the flat strip of inner fin 7.

According to FIGS. 2 through 4, strip thickness reduction R from L1 to L2 is carried out on both oppositely situated wide sides 13 of the flat strip of inner fin 7 by a constriction. For example, approximately the same amount of proportional strip reduction R1, R2 of approximately R1=(L1−L2)/2 and R2=(L1−L2)/2 is optionally carried out on both wide sides 13.

Correspondingly, strip thickness reduction R from L1 to L2 is proportionately present on both sides of the neutral fibers 14 of the strip of inner fin 7, in particular approximately the same amount of proportional strip thickness reduction R1, R2 of approximately R1=(L1−L2)/2 and R2=(L1−L2)/2 is present on both sides of neutral fibers 14. R=R1+R2 therefore applies.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims. 

What is claimed is:
 1. An inner fin for a flat tube of a heat exchanger comprising: a metallic flat strip formed in a wavy modulated manner; a plurality of wave crests and wave troughs formed in the metallic flat strip, the plurality of wave crests and wave troughts being arranged alternately in a longitudinal direction of the inner fin; and an essentially straight, web-like fin area formed between one wave crest and an adjacent wave trough, the web-like fin area connecting a wave crest to a wave trough, wherein the metallic flat strip has a first strip thickness L1, which is essentially constant in an area of the wave crests and the wave troughs, wherein the flat metallic strip has a second strip thickness L2, which is formed in the area of the web-like fin area, and wherein L2 is smaller than L1.
 2. The inner fin according to claim 1, wherein the metallic flat strip has a first strip thickness L1, which is essentially constant in the entire area of the wave crests and the wave troughs, and wherein the flat metallic strip has a second strip thickness, which is essentially formed in the entire area of the web-like fin area.
 3. The inner fin according to claim 1, wherein the metallic flat strip is curved in the area of the wave crests and the wave troughs.
 4. The inner fin according to claim 1, wherein the strip thickness reduction R from the first strip thickness L1 to the second strip thickness L2 takes place in a range from 0.2*L1 to 0.9*L1, i.e. 0.2*L1<L2<0.9*L1, in particular 0.3*L1<L2<0.7*L1 or further in particular 0.35*L1<L2<0.55*L1 or further in particular L2=0.5*L1.
 5. The inner fin according to claim 1, wherein the metallic flat strip has two oppositely situated wide sides, between which the strip thickness is determined, the strip thickness reduction R from the first strip thickness L1 to the second strip thickness L2 being carried out on at least one wide side of the flat strip or being carried out on both oppositely situated wide sides of the flat strip.
 6. The inner fin according to claim 5, wherein the strip thickness reduction R from L1 to L2 is carried out on both oppositely situated wide sides of the flat strip by a constriction, approximately the same amount of the proportional strip thickness reduction R1, R2 of approximately R1=(L1−L2)/2 and R2=(L1−L2)/2 being present on both wide sides.
 7. The inner fin according to claim 5, wherein the strip thickness reduction R from L1 to L2 is present on both sides of the neutral fibers of the strip, in particular approximately the same amount of proportional strip thickness reduction R1, R2 of approximately R1=(L1−L2)/2 and R2=(L1−L2)/2 is present on both sides of the neutral fibers.
 8. The inner fin according to claim 1, wherein the metallic flat strip has a first strip thickness L1, which is essentially constant in the entire area of the wave crests and the wave troughs, and the flat metallic strip has a second strip thickness L2, which is essentially formed in the entire area of the web-like fin area.
 9. A flat tube comprising: a tube wall having two oppositely situated wide sides and two oppositely situated narrow sides; a tube interior; and an inner fin according to claim 1, the inner fin being arranged in the tube interior, wherein the wave crests abut one of the two wide sides of the tube wall, wherein the wave troughs abut the other of the two wide sides or the wave crests connected to one of the two wide sides of the tube wall, and wherein the wave troughs are connected to the other of the two wide sides via, in particular soldered, welded or glued.
 10. The flat tube according to claim 9, wherein the wave crests are soldered on one of the two wide sides of the tube wall, and the wave troughs are soldered on the other of the two wide sides, wherein solder menisci made from solder material is formed between the strip and the wide sides, and wherein the web-like fin area has the second strip thickness L2 being arranged between the solder menisci. 